Re: [PATCH] qemu-sockets: fix unix socket path copy (again)

[Michael Tokarev]

On 01.09.2021 12:52, Peter Maydell wrote:
> On Wed, 1 Sept 2021 at 09:29, Michael Tokarev <mjt@tls.msk.ru> wrote:
...
> > We have sizeof(sockaddr_storage) space there. If the kernel returned
> > salen greather than that, this means we received only partial address
> > and can't rely on it. It is like snprintf() returning more bytes than
> > available in the buffer - it says how much bytes NEEDED.
>
> I think that if we need to check that we should be checking that
> at the point where we make the accept() or whatever other call
> filled in the sockaddr. That is the point at which the code
> either (a) knows that the buffer is guaranteed big enough and
> can assert that if it likes or (b) may have some reasonable way
> to deal with the failure, eg allocate a bigger buffer and retry,
> and (c) it is also the point where the code knows how big the actual
> buffer it passed to the kernel is and so can validly determine if
> it was truncated.

I don't care where it is done, as long as what is done does not
break in real-life scenario.

Originally I asked another question: WHY we ask for the socket name
in the first place, why do we need it, where do we use it?

Maybe we should answer to this one first and maybe remove whole
thing completely instead of fixing something which isn't used?

> We don't check that the address is not truncated in any of the
> other sockaddr-type-to-SocketAddress conversion functions...

Because other addresses have fixed length. If anything there does
not fit or is not equal to the expected length, the hell will break
loose for every application out there, qemu will note be the first
to look for..

/mjt